The present invention relates to diesel engines of the type comprising:                one or more cylinders and at least one intake valve for each cylinder, provided with elastic means that push the valve towards a closed position; and        at least one camshaft for controlling the intake valves by means of respective tappets;        wherein at least one intake valve for each cylinder is controlled by the respective tappet, against the action of the aforesaid elastic means, via hydraulic means including a pressurized fluid chamber;        wherein the pressurized fluid chamber is designed to be connected, by means of a passage controlled by a solenoid valve, with an exhaust channel, so that, when said solenoid valve is open, the intake valve is uncoupled from the respective tappet and is kept closed by the aforesaid elastic means;        there being associated to said engine electronic control means for controlling each solenoid valve in such a way as to vary the time and/or the stroke of opening of the respective intake valve as a function of the operating conditions of the engine.        
Some time ago the present applicant developed a system for variable actuation of the intake valves of the engine, identified by the trademarks UNIAIR and MULTIAIR (see EP-A-803 642, EP-A-0 961 870, EP-A-0 931 912, EP-A-0 939 205, EP-A-1 091 097, EP-A-1 245 799, EP-A-1 243 763, EP-A-1 243 762, EP-A-1 243 764, EP-A-1 243 761, EP-A-1 273 770, EP-A-1 321 634, EP-A-1 338 764, EP-A-1 344 900, EP-A-1 635 045, EP-A-1 635 046, EP-A-1 653 057, EP-A-1 674 673, and EP-A-1 726 790).